1. Field of the Invention
The present invention relates to a dye-sensitized solar cell to convert solar energy into electric energy by a photo-electrochemical process and to a fabrication method thereof, and particularly, to a dye-sensitized solar comprising a semiconductor electrode consisting of electrospun ultra-fine titanium dioxide fibers and to a fabrication method thereof.
2. Description of the Background Art
Since Grätzel's research group in Swiss has reported a dye-sensitized solar cell (B. O'Regan, M. Grätzel, Nature 353, 737 (1991)), researches thereinto have been actively conducted. The dye-sensitized solar cell by Grätzel et al. is a photo-electrochemical solar cell using an oxide semiconductor electrode comprising photosensitive dye molecules that can absorb light within visible region, thereby to generate an electron-hole pair and nano crystalline titanium dioxide that can transfer the generated electron. In this cell, electrons excited in dye molecules upon receiving light within visible region are transferred to titanium dioxide which is an n-type semiconductor, and dye molecules are reproduced through an electrochemical oxidation-reduction of I−/I3− contained in a liquid electrolyte, by which current is generated.
The dye-sensitized solar cell is much expected as a solar light conversion element due to its higher energy conversion efficiency, while its fabrication cost is relatively low compared to a conventional silicon solar cell.
However, because dye-sensitized solar cells provided until now include a liquid electrolyte, stability problems have been raised, and especially, because it is difficult for such solar cells to be sealed, the liquid electrolyte can be leaked or an electrochemical stability cannot be ensured in using the same for a long time. Recently, in order to resolve such problems, researches have been actively conducted for using an inorganic solid electrolyte (Langmuir 19, 3572 (2003)), a polymer solid electrolyte (Electrochemica Acta 47, 2801 (2002)), a gel electrolyte (J. Phys, Chem. B 107, 4374 (2003)), an ionic liquid (J. Am. Chem. Soc. 125, 1166 (2003)), an organic hole carrier (Science 295, 2425 (2002)) or the like, instead of using a liquid electrolyte. However, while a liquid electrolyte can easily infiltrate throughout an entire electrode plate having a thickness of 10 μm or more which is fabricated by sintering nanocrystalline titanium dioxide particles, it is difficult for a non-liquid electrolyte to infiltrate into such electrode plate, and therefore, energy conversion efficiency is lowered for cells using a non-liquid electrolyte compared to those using a liquid electrolyte (Chem. Lett. 30, 26 (2001); 31, 948 (2002)). Although a cell construction using a porous titanium dioxide thin film based on a sol-gel method or particles in rod shape has been proposed as a solution for such problems, it has been known that its performance is much inferior compared to the conventional nano-particle type. Therefore, there are problems yet to be solved.